Wave meter and similar electrical device



Mar. 13, 1923.

G. H. STEVENSON WAVE METER AND SIMILAR ELECTRICAL DEVICE Filed Dec. 21, 1920 Patented Mar. 13, 1923.

UNITED STATES GEO ROE H STEVENSON OF ltYii NE) YORK ASSIGNOR TO ESTERN ELECTRIC COM PANY, YNCORPORATED. OF NEW YORK, N Y A CORPORATION OF NEW YORK.

WAVE METER AND SIMILAR ELECTRICAL DEVICE Application filed Deccmhrr IL 1920 To allmliom it may concern Be it lfllOWn that I,.Gr;ur.i: ll. ru L.\\H.\ asubject of the King of (lrent llrurnn u: siding at Rye, in the count of \\'c lchc.-t.c

6 State of New ark haye invented cerium npw and ,useful [m rpveqients in \'ri\c h tcrs-.:ii1d S ir nilar lectrical Devices of w ichithe tollo yzingis a full. clear, concis and exactflcsgription.

l i inrcntiqnrelatcs t0 \tzu'nu ctei's aunl similar.electrieai appm'atus, and more particuhigly to. means whereby the frequency libljgti0lk9tt0 apparatus will not be dared incorrect ythc opening or closing Q ;.&.,l qy ..00nnected to the circuits of the apparatus. I; ,.It is eustomary in the arts dealing with high frcqiicncx c rrcnts when. \\':1 leu; [th grew be. n egisurc or comparcd,t o make use of a wavexnet er svhieh for some purposes oons stsof a. simplq tuned, rcceiyer and detoif qr hi ghifgcquency wai'cs and for o her pupbsesponmsts of a low power generator ,The;usual manner of changing the 26 appariitus to form locaLgeuerzgtor is '1:- includcin .circuitpbuzzer or-sclf-interruptingelectroniilgnct which causes the timed circuitof the wave-meter to he excited at its rfinant f-equcncy It hnshceu found that 30 key which scrtcsto connect the huzzm' the circiiit has a. c:ipacit y between its contact .hladcs of sullicienl ,mugnitudc uraiisc ,theewaye-lcngth calibration which is rprrcct,witli tlickcy opened to he incorrect when the ;key is closod or rice versus This h ppens because th qefl'ectivc capacity of the kev blades is in shunt with the tun ng eondei senof the tu ned circuit when the. key is Qpencd. 'Ilhlqcspacity, in a particular instance is of the order of lOxlO' fnruds. capacityof this magnitude produces, apprecilible efl'octs p't radio flmt pncics. By. placing additional insulated lades on the key and, connectingthcse additional blades in circuit so thiitnhen the key is closed their czip ncity will be substituted for the cllectiv capacity introduced hi the contact blades when the key is opened. the calibration inn) he made correct for either opcrnlivr con 50 ilitinii of the np uirnlu Serial No 432194 The inientnui \\'lll he described in detail Ill [(JIIIICLLH'HI \iilli lln u r ulnpunting drank in; wherein l'ig. I\ a circuit diagram in \(ll\ my the cssentmi natures of the llH'Cfl- Lion; and hug. 1. is a muss-sectional new of u cabinet in which the waive-meter is con- L-meil, slunvn the structure of the key and :i pnslr-lintton for operating il.

Referring to l' ig. l. the wavc-iueter circuit comprises iesouziut high frequency ci cuit including a coil 1 and .a suitable uriable condenser 2. The variable condens er is usually calibrated with .a scale which indicates wavelengths to which the tuned circuit will be resonant when it includes a coil l pfspecified inductance. detector 3, preferably eonsistingol' :1 crystal. 'of, vrites hut which may consist ofany suit/a. lc detector of the crystal thermionic or other type is connected across the terminals of the capacity 2 by a circuit 4. The circuit 4 includes a con denscr 5 whose capacity is small coinpa cd to that of the cqnder serifl. By placing theeondenser 5 in series with the deter-tor 3, the cfl'cct of the capacity inherent. in thcirlctectnr and its associated elements upon the tuning of the circuit [.2 is reduced to u negligihle degree. l,n the ease of a cir cnit dealing with th usual radio frequencies that is. from one hundred thousand in two million cycles er second. the capacity 5 should he of the order of l sh) [iii-ads. jncl; 6 is provided. h v means of which the telephone receiver or other suitable indicating instriuncnt may be connected around the detector 3.

The circuit :15 so [:1 r dcscrihcd may be used to determine the wave-length of electromagnetic ,waves by int oducing the coil 1 into the ficld of the wares whose frequency isto be determined and ,varying the condenser 2 until it maximum indication is obtained in the telephone receiver. The calibration of thc capacit 2 may be in wavcl s or in frequencies which ma b(- read all ircctly or, if preferred, in capacity units In) ihich the mic-length may be computed i the cnnstnnls of the (t ll I are known lllU i itv ellect of appreciable magnitude f e uency to \rliirh the (.ll'titllt l. '2 is resoiiant. For this purpose. a buzzer d in "111" till with the -onii'r i-tlll'tfil current I is rovided. l'eSlstance i l of about 1" ohms llltl\' advantageously be connected around the elcctroinagnet iii [llt' buzzer. hen the contact blades 11 of the l;e K aie closed. the buzzer is connected in shunt around the rondenscr The hux/er thereupon o erates and excites the circuit l. '2 thereby caus in (herein the lll'Utlllijll tt i-lriillliltltllfi of the frequency to which the circuit is resonant. lVhen the key N is opened. the blades 11 and 12 are separated and produce a input- 7 lllI(fC the capacity formed by the blades l1. 12 is connected in shunt to the condenser 2 through the circuit comprising the buzzer 8 and the source 9. the calibration of the con denser will not be correct when the her is closed if it is correct when the key is opened and vice veisa. The cleetroniagnet of the buzzer has a. large distributed capacity so that it forms together with the small re. sistance 10, a path of relatively low impedance to high frequency current whereby the capacity of the blades 11 and 12 produces its full effect upon the capacity 9, when the buzzer contact 20 is in its normal closed condition.

An additional set of blades 13 is provided for the key K. Blades 13 are spaced away from and insulated from the blades 11 by the insulating material 14. When the key K is closed, the capacity between the blades 11 and 13 is caused to be in shunt to the condenser 2, the shunt circuit being through blades 12, 11, 13 and conductor 15. If this capacity is of such magnitude as to be equal in effect to the capacity between the blades 11 and 12 when they are separated, the calibration of the condenser 2 will be equally correct whether the key K is opened or closed. WVhen the key K is closed. the capacity between blades 11 and 13 is short circuited through the buzzer circuit if the contact 20 of the buzzer is closed. However. oscillations are generated in the circuit 1, 2 substantially exclusively when the contact 20 is opened. The sequence of events is, first, closing of contact 20; second. increase of current flow through inductance l; third. opening of contact 20; fourth, production of a damped train of oscillations in circuit 1, 2. The oscillations in circuit 1, 2 fall to a negligible value by the time contact 20 closes again. High frc uency oscillations occur, therefore, principal y when contact 20 is open, during which time capacity 11-13 is in effective shunt to capacity 2. The small capacity bet een the terminals of contact 20 is neglected as this will in o an error too small to e considered :\s shown in Fig 3. the wave-meter as :i whole, except coil 1. is provided ith :in

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enclosing and \hielding calunri it; liaiiiig a hinged lid ii upon which a hlocl; 13 is mounted. \Yhen the lid ll} iraced. a pushhiitton 1 l accessible. lly pulling out or raising the button 19. the kei K may he closed. by pushing it in, the he) will he opened. hen the lid 17 is losed. the

block 13 is arranged to force the push-hutton 1.) rloun to the farthest e\tent thercbi' opening the liey K and preventing the wavemeter being put away with the l e left in"- cidentally closed so that the battery 9 would run down and become exhausted.

Although this invention has Iieen described as embodied in a \vave-iiieter it is obvious that the principle involved is capable of much broader application and all such applications are considered as falling within the scope of this invention.

\Vhat is claimed is:

l. :\n electric circuit including a circuit closing device having a normally open and a normally closed position, the elements of said device forming, when open, an electric condenser of capacity sutficiently large to interfere with the functioning of said circuit in combination with an element which substitutes a capacity of approximately equal value in the same electrical position in said circuit when said device is operated to close said circuit.

2. In a wave-meter, a tuned circuit containing a capacity element, a key in acircuit in shunt to said capacity element, two blades on said key forming a capacity in shunt to said capacity element when said key is opened, and an additional blade of said key forming a capacity of substantially e ual effective value in shunt to said clement w on said key is closed.

3. In a high frequency electrical apparatus a capacity element, a. circuit-closing element for closing a circuit in shunt to said capacity, said circuit-closing element when opened introducing a reactancc in shunt to said capacity element, and means automatically introduced in shunt to said capacity element by the closing of said circuit-closing element having an effective reactance substantially equal to the reactance'introduced by said circuit-closing element when opened.

4. In a high frequency electrical apparatus a capacity element, a circuit-closing element for closin a circuit in shunt to said capacity, said circuit-closing element when opened constituting, a ca acity in shunt to said capacity element, an means introduced in shunt to said capacity element by the clos ing of said circuit-closing element having an effective capacity substantially equal to the capacity of said circuit-closing element when it is opened.

5. A wave-meter comprising a tuned circuit. containing ii capacity element, a key for ISO connecting a buzzer in shunt to said capacity element, the blades of said key when opened constituting a capacity in shunt to said capacity element through a circuit including K said buzzer, and auxiliary blades on said key forming with at least one of said first mentioned blades, a capacity in shunt to GEORGE H. STEVENSON. 

